I'm no mechanic so don't take my suggestions for granted..
I had a stalling problem with my friend's Camry the other day..
Here are what I did:
1. Techron Concentrate (Try this stuff..) it's bout $5 from Autozone and dump it in the tank when it's almost empty to run it at high concentration.
2. Spark Plugs (cheap Bosch Supers... for the Camry hehehe) - make sure you get the right plugs.. I have heard bad things about the Platinum Plugs.. but you could always give them a shot. You could also try the expensive Denso Iridiums .
3. Fuel Filter
Either the first or the second fixed the problem.. the third was something we did because we had nothing better to do.. and gasoline stinks.. I prefer diesel smell heheh less strong..
Try the spark plugs, fuel filters, air filter, and techron first...
BTW what is the idle speed?
2008 BMW 335i Coupe